Normal functioning of the heart involves substantial deformation of the heart chambers in the cycle of systolic contraction and diastolic expansion. This deformation can be quantified in terms of mechanical strain, which is a deformation descriptor in terms of relative displacement of particles in the body that excludes rigid motion (measuring, for example, the displacement between points in the myocardium relative to reference positions of the points at a selected annotation time in the heart cycle). A number of pathologies in the heart, such as areas of ischemic cardiomyopathy (commonly referred to as “scar tissue”) and congestive heart failure, manifest themselves in abnormal (usually abnormally low) levels of strain or as abnormal timing distribution of strain. Such pathologies are most commonly evaluated by diagnostic imaging, using cardiac magnetic resonance imaging (MRI) or ultrasound, for example.
Mechanical functioning of the heart can also be measured invasively, using a mapping catheter that is inserted into the heart. For example, U.S. Pat. No. 5,738,096, whose disclosure is incorporated herein by reference, describes a method of constructing a cardiac map that includes bringing an invasive probe into contact with a location on a wall of the heart, determining, at two or more phases of the heart cycle, a position of the invasive probe, and determining a local non-electrical physiological value at the location. The method is repeated for a plurality of locations in the heart. The positions are combined to form a time-dependent map of at least a portion of the heart, and local relationships between changes in positions of the invasive probe and determined local non-electrical physiological values are determined. Preferably, local electrical activity at the plurality of locations is also acquired. The NOGA® system offered by Biosense Webster Inc. (Diamond Bar, Calif.) is configured for performing these sorts of measurements.
As another example, U.S. Patent Application Publication 2015/0228254 describes a method of generating an anatomical map, which includes acquiring geometry information and biological information for an anatomical region. The geometry and biological information are associated with each other, for example by associating measured biological attributes with the anatomical locations at which they were measured. A graphical representation of the anatomical region, including a map of at least two biological attributes, can then be superimposed upon a geometric model of the anatomical region.